The present invention pertains to digital switching networks with distributed processing control and more particularly to an arrangement for digital service tone distribution in a time switching network.
In distributed processing time switching systems, each time switching stage may be controlled by a separate central processing unit (CPU). In addition, at least one control CPU would be provided to instruct each of the CPUs of each time switching stages.
Previously in time switching networks, digital service tones have been inserted at the terminating time switching stage of the network for connection to its subscriber. Then, the terminating time switching stage would transmit a message to the originating time switching stage to return a similar service tone to the subscriber connected to it. In distributed processing arrangements, a number of interprocessor communications are required to accomplish this. The CPU of the terminating time stage must communicate the need for the application of tone to the control CPU. The control CPU must communicate to the originating time stage and instruct it to apply the particular tone. Then, the CPU of the originating time stage must acknowledge the application of the service tone to the control CPU. Then, the control CPU must return this acknowledgment to the terminating time stage CPU. A similar scenario would be performed for removal of the tone.
During periods of high traffic, this interprocessor communication tends to slow the effectiveness of the switching system. Furthermore, the switching system subscribers would notice a considerable delay in the application or removal of any service tone by the switching system.
Accordingly, it is the object of the present invention to provide an arrangement for digital service tone distribution in a multiprocessor controlled time switching network with minimal interprocessor communications.